Abused children will be at greater risk after the government abandoned plans to abolish expensive court fees, according to child protection experts.

The Law Society attacked the government's decision to rip up plans to drop what it calls "highly inflated fees" for childcare cases, warning that vulnerable children are at risk of being denied court protection.

The issue was subjected to acute scrutiny following the case of Baby Peter, the 17-month-old boy in Haringey who died as a result of abuse.

The previous government announced it would abolish fees altogether as of next April, following widespread opposition from children's charities. They claim the increase from £150 to more than £4,825, which came in during 2008, has had a negative impact on child protection.

In his report into child protection in the wake of the Baby Peter case, Lord Laming called for the rise in fees – described by Liberal Democrat MP Greg Mulholland as "a tax on keeping children safe" – to be reversed.

An independent report commissioned under the previous government also called for the fees to be scrapped after finding anecdotal evidence they deterred councils from applying to take abused children into care.

The report estimated that court fees for one council went up from £12,000 in 2007 to £300,000 in 2008.

However, the justice minister, Jonathan Djanogly, has announced the increase will not be reversed, saying users of the courts must pay. "There is no justification that these fees should be abolished," he said.

The decision has angered experts. "Setting court fees purely on the basis of cost may leave vulnerable children, particularly in cases of neglect, at greater risk of harm," said Desmond Hudson, chief executive of the Law Society.

"This move is even more serious now than when it was first introduced in 2008. It is local authorities who have to pick up the bill in these cases and they, like so many public sector bodies, are being squeezed by the chancellor." A report into Baby Peter's death found there had been an "unacceptable" lack of urgency on the part of Haringey council's legal team to issue care proceedings.

Applications for court proceedings to take children into care have increased by 40% at some councils since the case in November 2008. But the rise has caused a financial headache for councils. The Ministry of Justice gave them £40m to cover the increase but some councils claim this covered only half their costs.

"The decision not to abolish family court fees at a time when councils are under financial pressure is disappointing," an NSPCC spokesman said. "There is a serious risk that fewer cases will now go to court so denying vulnerable children and families justice."

A Ministry of Justice spokeswoman insisted the protection of vulnerable children was paramount for the government. "Where children might be at risk from harm, councils are legally bound to investigate and put any cases before the courts as swiftly as possible."

The spokeswoman said it was now up to councils to fund court proceedings through a block grant allocated to them. But Christina Blacklaws, an expert on child protection cases, said: "It doesn't reflect well on our society when we subject child protection to these sorts of financial pressures."